RF communications systems are well known in the art. In many such systems, as in public safety applications, vehicles are equipped with mobile transceivers that allow public safety officers to communicate with one or more base stations and also with other similarly equipped vehicles in the system. With reference to FIG. 1, such a mobile based system typically includes a vehicle (E) mounted transceiver (A), microphone (B), control head (C), and antenna (F). In addition, a base station (G) communicates with the vehicle mounted equipment and typically serves as a message dispatch center. As the situation may require, repeaters (not shown) may be provided to extend the effective range between the mobile and base station, all as well understood in the art.
The above configuration works well, so long as the public safety officer (or other individual) remains in the vehicle (E). Once the officer moves beyond the operational range of the microphone (B), however, the officer typically loses the ability to forward communications to the base station (G). Since the range of the microphone (B) will usually be governed by the length of the microphone cord (H), and since this cord (H) must usually be relatively short, communications remote from the vehicle (E) are usually rendered difficult if not impossible.
To meet this problem, portable transceivers (I) can be used to allow the officer to be able to communicate with the base station (G) when separated from the vehicle (E). The portable transceiver (I) must, in order to be effective, emulate the vehicle mounted system in all relevant aspects, including frequency capabilities, power rating, and signalling capabilities. In effect, a public safety service that implements this system must provide two wholly and independently functioning radio systems for each of its vehicles. Though this adequately supports the desired communication function, this solution also represents a relatively costly approach.
There therefore exists a need to provide relatively inexpensive, effective, and reliable communications for public safety officers and others who ordinarily make use of a vehicle mounted transceiver but who must also carry out operations away from the vehicle from time to time.